On 3 Dec 2005 09:44:04 -0800, "Fritz"
wrote:

My charger for my cordless drill recently stopped working. My drill is
dead as a doornail, and I've got projects pending. It's an off-brand
(Master Mechanic), and I've had some difficulty locating the
manufacturer. Efforts to purchase a new charger have gone nowhere.

So...I was able to determine that the fault lies with the AC/DC
converter ("wall-wart"). It's rated at 200mA and 14.5VDC, but at the
moment it's putting out essentially 0VDC (verified with my
multitester). I went to Radio Shack and purchased a 15VDC 1A wall wart,
with the intent of cutting and splicing it to the charger, but when I
tested it's output myself, it's actually kicking out 20.33VDC. This
seems high.

Before it was broken you could have measureed the output of the
original converter, with nothing attached, and it too would have been
a lot higher than the rating. (If you really need convincing, you
could buy another one with a drill and later return it, or even just
plug one in at the store, and measure it there.)

The output, the secondary winding of the transformer in the converter
itself has its own resistance -- I guess it would be called internal
resistance -- and when current flows through that resistance, there is
a voltage drop, even when measured before it reaches the wire that
goes to the charger.

If all it is is that the cord is broken inside, it's also possible
that you can repair the old one. Take a hat-pin or two** and shove
it into the wire until it hits the copper. Then check with your meter
again

**Or even a small pin or needle. Hat pins are better because they
have "handles". There are occasional short pins that come with "big"
knobs on the end. They come with corsages and various other things.
When you get these save them for this purpose. Mine are in my sewing
kit.

What happens if I solder a 20.33VDC output to a charger that's used to
operating with 14.5VDC? Will it damage the battery? Cause an explosion?
Other deleterious effects?

Radio Shack also had a (rated) 12VDC wall-wart. If it runs hot like the
15VDC version does, I might actually get pretty close to 14.5VDC. Would
that be a better idea? Do the outputs from these low-grade AC/DC
converters always vary that much from their rated output? And does
anyone sell converters that will match the OEM one fairly closely?

ff


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